Lockout mechanism for intercommunicating telephone systems



T. H. NELSON. LOCKOUT MECHANISM FOR INTERCOMMUNICATING TELEPHONESYSTEMS.

APPLICATION FILED OCT. 21,1918- lmwmo mama June 113, .1922.

2 sums-sum 1.

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APPLICATION FILED OCT. 21. 1918.

w Mm M ELAlQAEQSD' THEODORE H. NELSON, 03E CHICAGO, ILLINOIS.

LOCKOUT MECHANISM FOR INTERCOMMUNICATING TELEPHONE SYSTEMS.

Application filed October 21, 1918.

To (ZZZ 207mm it may concern:

Be it known that I, THEODORE H. hlnLsoN, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented certain new and useful improvement in Lockout Mechanisms forTntercommnnieating Telephone Systems, of which the following is aspecification.

li iy invention relates to an improved lockout mechanism adaptedparticularly for use with intercommunicating telephone systems by whichwhen one of the lines of the system is connected with another line forconversation, itis impossible to actuate selecting and switchingmechanism at a third station to connect the line of said third stationwi;h either of the bus; lines. More specifically, my invention consistsof a combined selecting, switching and lockout mechanism provided withreleasing devices by which, after using a desired connection, when thereceiver is placed on the switch hook of either of the connectedstations, the associated selecting and switching mechanism is restoredto neutral condition. in this respect my present invention constitutesan improvement on the invention disclosed in l nited States LettersPatent $21,290,645, which were issued to me January '7, 1919, whichshows releasing mechanism of the hind referred to, but no lock-outmechanism.

My invention, as described below, is equally applicable to systemsemploying either two wire lines or three wire lines and the presentinvention includes the system of either kind of which the loclroutmechanism is a part well as the look-out mechanism itself. .lvTVinvention will best be understood by reIerence to the accompanyingdrawings showing preferred embodiments thereof. in which Fig. l is adiagrammatic view of a threewire system involving my improved lockoutmechanism,

Fig. 2 is a vertical sectional view of the lock-out mechanism employed.in the system of Fig. 1,

Fig. 3 is a front elevation of the mechanism shown in Fig. 2,

F 4 is a sectional view of the parts shown in Fig. 2 taken along theline 4l4l in F ig. 2,

Fi 5 shows in a view similar to Fig. 1, a two-wire system involving myinvention and Fig. 6 's a detail sectional view of the Specification ofLetters Patent. Pgstgnigefl Jung 13, 1922,

Serial No. 259,019. s

modification required in the mechanism shown .in Figs. 2, 3, and 4ttoadapt it for use in the system shown in Fig. 5.

Similar numerals refer to similar parts throughout the several views.

Referring to Figs. 2, 3 and 4, my lock-out mechanism consists of acasing 10 having a removable front plate 11, to which the switching andloclcout mechanism is secured. Centrally disposed in the front plate isa plunger 12, to the outer end of which a dial 13 is secured. The dialis contained in a cylindrical recess formed by an annular flange14lprojecting from the front plate and may be rotated to select adesired line and then moved longitudinally of the plunger to first testfor a busy line and automatically operate the look-out mechanism if thedesired line is busy thereby preventing further movement of the plungerto connect withtlie desired line, second to connect with the desiredline if it is not busy, and third. by continued movement to send ringingcurrent over the connected line. The dial is normally held in its outeror neutral position by a spring 15 and motion to connect the lines isprevented. unless the dial is in proper angular position, by arearwardly projecting pin 16 carried by the dial and coope rating spacedholes 1? in the front plate arranged angnlarly relatively to the linecontacts so that longitudinal motion of the plunger is permitted onlywhen the dial is in an angular position bringing the connecting switchblades and the line contacts into alignment.

The front plate 11 has secured theretoand. projecting rearwardlytherefrom, posts 18 which support at their rear encs a contact plate 19of insulating material held in place, on said posts preferably by springcatches 20 or equivalent. means, so that. the contact plate may bereadily removed from said posts and front plate to permit the cont-actplate to be wired. into the system when it is installed, withoutrequiring the installation at the same time. of the front plate and themechanism carried thereby, which need not be done until the system isready for testing. The contact plate is in effect a terminal plate ofthe system for each station, and has mounted thereon a set of contacts21 for each line of the system, there being three of these contacts ineach set, and three contact rings 22, 23 and 24 for connection with theline and circuits of the station where the switching mechanism islocated. The inner end of the plunger 12 has secured thereto andinsulated therefrom, three switch blades 25, 26 and 27 for connectingthe rings 22, 23 and 24 respectively with the outer, the middle and theinner line contact 21 of any desired set, when the plunger is pushedinwards. The plunger has rigidly secured thereto, a disk 28, foractuating through insulating blocks the contact springs 29, 30 and 31,which are mounted upon and insulated from. the front plate. The contactspring 29 is placed under tension for the neutral position of theplunger by the action of the spring 15, and'when the plunger is pushedin, said contact spring follows said inward movement to first engage thecont-act spring 32 which is in engagement with the contact spring 33,and to then move the spring 32 from engagement with the'spring 1nwardmovement of the plunger also moves the spring 30 to engage the contactspring 34 and at the end of said inward movement, the spring 31 is movedto engage the contact spring 35. The contact springs 32, 33, 34 and 35are mounted upon and insulated from the front plate in operativerelation to the springs 29, 30 and 31 to secure the results described.it pivoted latch 36 rests upon the disk 28 to engage said disk in theline connecting position of the plunger to prevent outward movement ofsaid. plunger and the parts carried thereby during a conversation. Sai dlatch forms the armature of the releasing magnet 37, carried by thefront plate, and is pivotally connected to the yoke of said magnet at38. The plunger 12 carries adjacent the disk 28, a. sleeve 39 rotatableon said plunger but prevented from movinglongitudinally thereon by a pin40 in saidplunger. The rear end of said sleeve has an upwardlyprojecting arm 4:1 extending through a slot 42 (shown in Fig. 4:) in therear end of the latch 36. Said arm has extending through its upper end apin as, in a plane above lugs 441-. projecting upwardly from the latch36, when said latch is in its lower position. /Vhen said latch is in itsupper position however, said lugs lie in the path of the pin l3 andprevent movement of the plunger rearwardly a sutlicient dis tance tobring the switch blades and 27 into engagement with the correspondingcontacts 21 and rings 23 and 24;, if the plunger were in its neutralposition at the time of raising said latch.

The parts described are so proportioned and related that a smallmovement of the plunger inwards from its neutral position, results inclosing the contact springs 29 and 32 and at the same time connectingthe outer contact 21 with the ring 22. The ring 22 and contacts 29 and32 are connected with the magnet 37 in a manner to be described suchthat if at this time battery potential is on the outer contact 21, themagnet is energized and the latch 36 is at once raised to preventfurther inward movement of the plunger by the enga 'ement of the pin 43against the lugs l4. f the outer contact 21 is free from batterypotential, the plunger may be moved further inwards tobring the switchblades 26 and 27 into engagement with the corresponding contacts toconnect the lines for conversation in a manner to be described, and atthe same time the lug 15 on the latch 36 drops in front of the disk 28to prevent disconnection of the lines until the latch is raised. Thecontacts 30 and 34 may be closed any time as long as they are closedwhen the plunger is in its position to connect the lines forconversation. At this time the contacts 31 and 35 are still open and maybe closed by further inward movement of the plunger after which uponreleasing the pressure on the plunger, the spring 15 moves the plungeroutwards to its locked-in position again opening the contacts 31 and 35.This is to provide for ringing the called line in a manner to bedescribed. At the end of a conversation, the magnet 37 is energized bythe operation of the corresponding hook switch in a manner to beexplained and the latch 36 is raised freeing the plunger which, underthe action of the spring 15, is thereupon restored to its neutralposition together with the parts carried thereby.

In the system shown in Fig. 1, three stations are shown which representany three stations of the system, for example stations 3, t and 5, andfor each station line wires extend through the system as shown at L". Land L, each line being of the three wire type. is the stations are thesame and connected in the same manner to the system it will be necessaryto describe but one of them, as for example. the station iand theconnections made to its line wires L"; The terminals 1 and 2 of thetelephone set are connected with one terminal of the impedance windingsl6 and ii, the other terminals of which are connected with the terminalsat and 3 respectively of the telephone set. The terminal 3 is alsoconnected with one terminal of the signal bell at by wire 419. with oneterminal of the primary winding of the iraluction coil by wire 51., andwith the contact spring 35 of the switching mechanism by wire Theterminals l a, 6 and 7 are connected by wires 53, 5s and 56respectively, with springs 57, 58, 59 and 60 of the hook switch. Theterminal 5 is also connected by wire 61 with the spring 31 of theswitching mechanism andv this wire is connected by wire 62 with oneterminal of the magnet 37. The other terminal of the primary winding 50is connected with one terminal of the transmitter 63, the other terwiththe terminals of the receiver 70. '5 construction or the hook switch 18s1 1 ti with the receiver on the hook 71, the springs and ($6 engageeach other and all th other sprin are out of engagement with th adjacentrings, and wh n the hook 7'1 is i r osition as result of removing th Itrim the hook, the springs 59 and (it; enient. with each other, the and65' "e in engagement with (56 is out oi en 'arg'e- The other ninalinected by wire 72 with 9 and 30 of the switch he contact spring 3. ofonnected by wire 22 of the sw'tching 1nechaact spring is not connectedwith the wiring l e system.

terminals i t or the elephono et l and T5 with negahe and positive battry supply wires 76 and Ti" respectivelv, extending through the systemvfrom tl terrn he talking hatter}; It. I 'lh lare conilGC QLt f wires eires and. a or 1' e if. min and G are eonnectcl hy wires and 52 withpositive battery supphi wires 83 and 84- respectively, extendingthroitiggh the sy tem from the terminals of the signalling battery 85.The terminal '7 is connected by wire 86 with wire c of line L. .srs 1result the connections just desiribed, it will l, observed that thewires (1 and Z) of line are subjected to el ctrical potentia at alltimes from battery 78 through impedance coils 436 and s 1 whether thehook Tl is in its np er or lower position. The wi c of line If is howevr, tree from batter potential of any kind whei the hook 7 t 2 ndnegative in its position. since the spring 00 co ine cteal with is atthat tune lice Elem all at the ot t it When springs of the hook SWILC'nosed tie s 'ing (30 b en- 1e spring 59. connects \v'll't': a id thinwire 0 is sub ected t tron] the ba tery s placed upon the wire cloci-t-ont mechaa manner to be "l time the calling; station with stationthe latter; in conversation with is system. and c of line L are conoT, 8and 89 with the inner,

the middle and the and 24: respectively of the switching in chan roachst tion thus is in permanent its own line and it is not ecessaw toconnect a line to the contacts c l is not busy. o select the desiredline, say line L l 53, and the dial is depressec. connects the springs29 and 32 sai 1e time connects the outer conthrough switch blade withconnecting wire 0 of line L i 37 over the following path: wire a wire92, contact 2], switch blade 25, ring a) wire 73, spring 35 spring 232,spring 59, wire to magnet 37. it this time there is no potential on wireand there is therefore no action of the magnet to prevent turt-herinward movement of the dial. Coin tinned increment of the dial separatesthe springs and to open the path above traced to prevent subseqi'ientlyapplied. potential on the wire 0, resulting from the response oi thecalled station, reaching the magnet 32'. At the same time connection isestablished between springs and 34: the switch blades 26 and )7 connectthe middle 23 and and in; or contacts 21 with the rin 's Joly for whichposition the dial are still open. To signal station 5 the dialis movedrther inwards which closes sprin s 1 35 and current flows through the tpath: battery 85, wire 83, wire 81, ll 5, wire (3i, spring 31, spring35, terminal 2%, wire 7.), wire 93, ring 23, v-. itch blade as, middlecontact of set 0,

wire to 0t line L, thence to and through connections at stationidentical with. the corresponding path through the connections atstation lfrom wire Z) of line L which may be traced as follows: wire Z)of line If, wire I 9 terminal 3, wire 4L9, bell 4:8, wire 6'1 spring 66,spring wire terminal 6, wire 82, wire 84: back to battery "F-Jlrenstation 5 re the receiver from the toe connection is in talkingcondition,

1 talking on:-

disconnect the hr spends by reinovin i i.

wir

nations being supplied wit yer ident 1 c: l 1):

ill;

both s I i ghs which maybe traced toliows: hatl y 78. wire ii. wire in,tein. l fo 'npedance coil ll. i-minal 3. wire (ii iary winding 50, titer(323., wire or spring spring 57,

I renn n jance coil 4L6, ter- 3 ot stations: SlllillQtS wire c of itsline to nega tive pOiOidllttl. from sigg nallingr battery 555 over asimilar path which may be trace for station 4 as follows: hz ry 85, wire8 wire 'li, terminal (3, wire spring spring (30, wire 56, terminal 7, wie 86 wire 0.

All QllO end oi the conversation. -.ach switching mechanism isautomatically rele rml am restored to neutral or hiilil'lfih conditionby the hanging up of the receiver at the corresponding station asfollows: When the receiver is placed on the hook T1, current is ceasedto take the "following path through niagniot 5:3? battery 85, wi 88,wire ill, terminal 5, wire 6L wire (52.. magnet 34, wire 72. spring;:30, spring 34-. n 68. wire (37. spring (56. spring 59. W11" 55,terminal (3.,

wire 82, wire 84- back to battery 85. This energizes magnet 53'! thusraising; the latch 36 and releasing the plunger l2 and the spring' 15moves said plunger and parts connected therewith to their outer orneutral positi on Assume now that station '1; desires to connect witheither station 5-, o 5 while they are connected and their lines arebusy. For this endition, as pointed out above the wires (2 ollines Land. if are subjected to negative potential lroin battery Slay that itis attempted to connect with station 'lhe dial 13 at station 4-. isrotated to position 5 and irissed inwards. The IHOHMJlt it is depressedenough to connect the springs 29 and 32 and to connect the outer contact21 with ring; through switch blade E25, current is caused to take thefollowing iath: wire 6 0t line if: wire J2 outer contact 2i oi setswitch blade :25, ring wire (3, spring 33, spring 32, s iiring 29. wire72, magnet 37} wire c2. wire 6'1. tern'iinal 5, wire til, wire 88 backto battery 85. This energizes inagnet 3'? which at once moves the lugs4:41: into the path oi? the pin 18 and prevents further inward motionoi? the dial. 13 and parts connected therewith and thus preventsconnecting line T14 with line if. The thing occurs on attempting toconnect with any busy line.

ninals i and coi'inected as before impedance coils with the terminalsind o esoectively. instead oi being conwi'l the talkii'ig battery. theterniiis col 1 c l by wire who spring 96 hook swatch which spring whenthe oi the hook: is raised engages spring 5)? connected by wire 98 withterminal. '5, .ani tern'nnal be ing connected in turn by wire 99 withwire lot) extending through the system from the negative terminal of thetalking battery T8 The transmitter and induction coil. primary windingare connected together before but in this case their tern'iinals areconnected directly with the terminals 3 and 4i; so that when both of theterminals 3 and 4t are subjected to battery potential of opposite signcurrent will flow through the transmitter. The terminals 3 and i areconnected with switching; mechanism much in (to the rings oi. thethesanr as before the only difference being that they are connected withthe outer and middle rings 22 and 23% instead oi, being connected withthe middle and inner rings. .lfi i'oin the above it will appear that theterminal l, connected through its impedance coil. with terminal l, isnot normally subjected to potential of any kind and that when lhe hool-zis raised, it is subjected to negative potential, from battery 78. Theterminals 3 and are connec'ied by wires lOl and 1()2 with wires 2) and arespectively of line l1 and these wires UH. and 1.02 are connected bywires 103 and ill-" with the rings 22 and 23; Since there are but twowires for each line there are but two contacts 521 in each set and theseare connected at each station with the line wires of the correspondingline in the same manner as before ti e contacts correspondino to eachstation not being connected at that station to its line tor the reasonspointed out above in con nection with. Fig. l. The terminals 53 and (iare connected as before with the exeiition that the terminal 5 is notconnected with the hook switch which however, makes no difference in theoperation ot ti. o present systen'i. The spring contact 33 of tieswitching mechanism is connected by wire 107 with the inner ring 24* ofsaid mechanism. In other respects the connections to the switchingmechanism are the same above described.

In this case the construction of the switching mechanism is modifiedsomewhat as shown in Fig. 'l he plunger carries switch blades 25', 26 ad 27*. insulated from each other and from tl e plunger for engaging therings 23 and iii respectively. in addition a fourth blade 26" issimilarly carried by the plunger. he blades 26" and are normally incontact with each other, the blade 26' being extended to engage theinner contacts 21 while the blade 27 is shorter and lies inside of theinner contacts 21 The blades 26 and 26 are normally out of contact witheach other, which condition is maintained until the plunger is depressedsutliciently to bring the blade 25 into engagement with the outercontact 21 and the ring 22 at which time the plunger and parts carriedthereby are held in their line connecting position by the lockingmechanism above described. F or this condition of the mechanism, theblades 26* and 26" are in contact and connect the inner contact 21 withthe ring 28, and the blade 26 is out of con tact with the blade 27 Inother respects the switching mechanism is oi? the same con struction andoperation as that shown in Fig. 2. lVith the construction shown in Fig.6, the initial movement of the plunger to test for a busy line. connectsthe inner contact 21 with the ring 249 through blades 26* and 27 andthus connects the wire a- 01' the called line with the wire 107 as shownin Fig. 5. It now the wire 100 from the negative side of battery 78 isconnected with said wire a as a result of the called line being busy, inthe manner above described, the locleout mechanism is operated bycurrent flow over the following path: battery 78", wire 10S. ground 109,ground connection 110, ground 11.1., wire 112. wire 1.13, wire ill,terminal 5, wire 61, wire (32, magnet ii. wire '72, spring 29, spring3%, spring 33. 3". wire 10?, ring 2%, blade 27 blade 26 inner contact 21wire a of called line and thus to wire 100 and baclr toba-ttery 78 is are sult the lock-out mechanism above described is actuated by theenergizing of the magnet 37, and further movement oi? the plunger 1%towards its line connecting position is prevented. In this case, asbefore, the plun ger has three operating positions which tollow eachother progressively, first, the line testing position which operates thelock-out mechanism if the called line is busy, second. the lineconnecting position and third, the signalling position. In the lineconnecting and signalling positions of the plunger. the effect is thesame as described in connection with Fig. l, and at the end of aconversation the releasing of the switching mechanism at each station iseffected in the same manner as before.

By my invention. it will be observed that I provide line wires o1 whichat least one is not subjected to potential iii the line is not busy.which wire has potential on it whe the line is busy which operateslock-out de vices to prevent actuation of line conne :ting switchingmechanism at another station, it an attempt is made at the latterstation to connect with the busy line; that the loc ut mechanism is apart mechanically o switching mechanism, and more s iiecifically that itand the releasing mechanism ot the switching mechanism have commonoperating devices; and that the lock-out mecha nism may be employedeither in connection with the releasing mechanism or without as desired.

l Vhile I have shown my invention in the particular einbodii'nents abovedescribed, I do not however limit myself to these constructions as I mayemploy any equivalents known to the art at the time of the filing of Uthis application without departing from the scope of the appendedclaims.

F -That I claim is:

1. In an interconiniunicating telephone system, the combinatimi oi":stations. each cquip 'ied with a telephone set, a switch hook and lineconnecting mechanism. lines for connecting said stations as desired, onewire of each line being free from electrical potential when not in use.a source of current, and contacts operated by the switch hook at eachstation for connecting said wire of the corre sponding line with oneterminal of said source for the busy condition of said switch hook. saidmechanism comprising contacts for said lines electromagnetic devicesconnected with the other terminal of said source and lock-out contactsactuated by initial movement oit said mechanism in attempting to connectwith a busy line. for connecting said. wire 01 said line with the otherterminal of said devices to actuate said devices to block completii'ithe line connecting move ment of said mechanism.

2. In an intcrcoi'nmunicating telephone system. the combination oilstations. each equipped with a telephone set. a switch hook and lineconnecting mechanism. lines for connecting said s ions as desired, onewire of each line being 'ee from electrical potential when not in use. asource of current. and cont-acts operated by the switch hook at eachstation for connecting said wire ot the corresponding line with oneterminal of said source vtor the busy condition of said switch hook,said mechanism comprising contacts for said lines. electromagneticdevices connected with the other terminal of said source and lock-outcontacts actuated by initial movement of said mechanism in attempting toconnect with a busy line, for connecting said wire of said line with theother terminal of said. devices to actuate said devices to blockcompleting the line connecting movement of said mechanism, continuedmovement oi said mechanism in connecting with a non-busy iine openingthe connection made by said lock-out contacts.

3. In an intercommunicating tQlQj llUllQ system, the combination. oistations, each equipped with a telephone set, a switch hook and lineconnecting; mechanism, lines tor connecting said stations as desired,one wire of each line being "free from electrical potential when not inuse, a source of current, and contacts operated by the switch hook ateach station for connectingsaid wire of the corresponding line with oneterminal of said source for the busy condition 01'' said SYv'ltL'l'].hook, said mechanism comprising contacts for saidv lines, a plunger,switch blades tor connecting the line contacts desired, a latchpermitting initial movement oi said plunger and. when operatedpreventing fur ther movement thereof to its line connecting; position,an electromagnet for operating said latch connected with the otherterminal. or said source, and lock-out contacts actuated by said initialmovement for wnnectine said wire of a busy line with the other terminalof said electromagnet to operate sa d latch when attempting to connectwith a lousy line.

4. In an intercommunicating telephone system, the combination ofstations, each equipped with a telephone set, a switch hook and lineconnecting mechanism, lines for connecting said stations as desired, onewire of each line being tree from electrical potential when not in use,a source of current. and contacts operated by the switch hook at eachstation for connecting said wire ot the corresponding line with oneterminal of said source for the busy condition (it said switch hook,said. mechanism comprising contacts for said lines. a plunger, switchblades for connecting the line contacts as desired, a latch permitting;initial movement of said plunger and when ope 'atcd preventingfurthermovement thercoii to its line (()!lnecting position, an electromagnettor operating said latch connected with the other terminal 0t saidsource, and lOCAC-Ollt contacts actuated by said initial movement torconnecting said wire of a busy line with the other terminal of saidelectromagnet to opcrate said latch when attempting to connect with abusy line. continued movement of said plunger in connecting with anon-busy line opening the connection made by said lock-out contacts.

5. In an intercommunicatii1g telephone system, the combination oistations. each equipped with a telephone set, a switch hook and lineconnecting mechanism, lines tor connecting said statio as desired, onewire of each line being free from electrical potential when not in use,a source of current, and contacts operated by the s itch hook at eachstation for connecting said. wire oi the 1,4,1 ones corresponding linewith one terminal of said source for the bus condition of said switchhook, said. mechanisn'i comprising contacts for said lines,electromagnetic devices connected with the other terminal of said sourceand lock-out contacts actuated by initial movement ol said mechanism inattempting to connect with a busy line, for connecting said wire of saidline with the other terminai of said devices to actuate said devices toblock completing the line connecting movement of said'mechanism, saiddevices ser"- ing' to also retain said mechanism in its line connecting;position on connecting with a non-busydine, and switch hook contacts andconnections at the corresponding station. a c

tuating said. devices on movement of said switch hook to its non-busyposition to re lease said mechanism.

6. in an intercommunicating telephone system, the combination oistations, each equipped with a telephone set, a switch hook and lineconnecting mechanism, lines for connecting said stations as desired, onewire o l each line being tree "from electrical potential when not inuse, a source Oil current, and contacts operated by the switch hook ateach station tor connecting said wire of the corresponding line withvone terminal of said source tor the busy condition of said switch hook,said mechanism comprising contacts for said lines, electromagneticdevices connected ith the other terminal of said source and. lock-outcontacts actuated by initial movement of said mechanism in attempting toconnect with a busy ine, for connecting" said wire of said line with theother terminal of said devices to actuate said devices to blockcompleting the line connecting movement of said mechanism, continuedmovement of said mechanism in connecting with a non-busy line openingthe connection made by said lock-out contacts, said devices serving toalso retain said mechanism in its line connecting; position onconnecting with a non-busy line, and switch hook contacts andconnections at the corresponding station actuating said devices onmovement of said switch hook to its non-busy position to release saidmechanism.

7. in an intercomnuinicati11g telephone system, the combination ctstations, each equipped with a telephone set, a switch hook and lineconnecting; mechanism, lines for connecting said stations as desired,one wire of each line being free from electrical potential when not inuse, a source of current, and contacts operated by the switch hook ateach station for connecting; said wire oi the come spending line withone terminal of said source tor the busy condition ot said switch hook,said mechanism comprisingcontacts tor said lines, a plunger, switchblades for connecting the line contacts as desired, a latch permittinginitial movement of said plunge and when operated preventing :turthermovement thereoi to its line connecting pos"'on, an. electr a net toroperating said latch connected with the other tcrminal oit said source,and lock-out contacts actuated by said initial movement For con- 7 wireo'l a )usy line with the Mil of said electreiuagnet to op said ch whenattempting to con neci with a busy line, said latch serving to alsoretain said plunger in its line connectin position on connecting with anon-busy line, and switch hook contacts and connections at thecorresponding station actuating said electromagnet on movementof saidswitch hook to its non-busy position to op crate said latch and releasesaid plunger.

8. in an intercommunieating telephone system, the combination ofstations, each equipped with a telephone set, a switch hook and lineconnecting mechanism, lines for connecting said stations as desired, onewire oi each line being free from electrical potential. when not in use,a source of current, and contacts operated by the switch hook at eachstation tor connecting said wire oi the corresponding line with oneterminal of said source tor the busy condition of said switch hook. saidmechanism comprising contacts tor said lines. a plunger, switch bladesfor connectin the line contacts as de sired. a latch permitting initialmovement of said plunger and when operated preventing 'turther movementthcrco't to its line connecting position. an electroinaguet foroperatingsaid latch connected with the other terminal ot said source,and lock-out contacts actuated by said initial movement for connectingsaid wire of a busy line with the other tern'iinal ot saidelectroinagnet to operate said atch when attennpting to connect with abus line. continued movement of said plunger in connecting with anon-busy line opci'iiug the connection made by said ock-out contacts.said latch serving to also retain said plunger in its line connectingposition on connecting witha non-busy line, and switch hook contacts andconnections at the corrcspoiuling station actuating said clectromagncton unwcment oi said switch hook to its non-busy position to operate saidlatch and release said plunger.

5). in an interconimunicating telephone system, the combination ofstations, each equipped with a telephone set. a switch hook and lineconnecting mechanism. lines for connecting said stations as desired,each line consisting of but two wires. one wire of each line being treefrom electrical potential when not in use. a source of current, andcontacts operated by the switch hook at each station for connecting saidwire of the corresponding line with one terminal of said source for thebusy condition of said switch hook, said mechanism comprising contactsfor said lines, electromagnetic devices connected with the otherterminal of said source and lock-out contacts actuated by initialmoveniei'it or said mechanism in attempting to connect with a busy line,for connecting said wire oi" said line with the other terminal. of saiddevices to actuate said devices to block completing the line connectingmovement of said mechanism.

10. In an intercommunicating telephone system, the combination ofstations, each equipped with a telephone set, a switch hook and lineconnecting mechanism, lines for connecting said stations as desired,each line consisting of but two wires, one wire of each line being freefrom electrical potential when not in use, a source of current, andcontacts operated by the switch hook at each station for connecting saidwire of the corresponding line with one terminal of said source for thebusy condition of said switch hook, said mechanism comprising contactsfor said lines, electromagnetic devices connected with the otherterminal of said source and lock-out contacts actuated by initialmovement of said mechanism in attempting to connectwith a busy line, forconnecting said wire of said line with the other terminal of saiddevices to block completing the line connecting movement of saidmechanism,- continued movement of said meehai'iism in connecting with anon busy line opening the connection made by said lock-out contacts.

11. In an intereommunioating telephone system, the combination ofstations, each equipped with a telephone set, aswitch hook and lineconnecting mechanism, lines for connecting said stations as desired,each line consisting of but two wires, one wire of each line being freefrom electrical poten tial when not in use, a source of current, andcontacts operated by the switch hook at each station for connecting saidwire of the corresponding line with one terminal of said source for thebusy condition of said switch hook, said mechanism comprising contactsfor said lines, a plunger, switch blades for connecting the linecontacts as desired, a latch permitting initial move-- ment of saidplunger and when operated preventing further movement thereof to itsline connecting position, an electromagnet for operating said latchconnected with the other terminal of said source, and lockout contactsactuated by said initial movement for connecting said wire of a busyline with the other terminal of said electromagnet to operate said latchwhen attempting to connect with a busy line.

12. In an intercommunicating telephone system, the combination ofstations, each equipped with a telephone set, a switch hook and lineconnecting mechanism. lines for connecting said stations as desired eachline consisting of but two wires, one wire of each line being tree fromelectrical potential when not in. use, a source of current, and contactsoperated by the switch hook at each station for connecting said wireoithe corresponding line with one terminal of said source for the busycondition oi": said switch hook, said mechanism comprising contacts torsaid lines, a plunger, switch blades for connecting the line contacts asdesired, a latch permitting ini tial movement oi said plunger and whenoperated preventing further movement thereof to its line connectingposition, an electromagnet for operating said latch connected with theother terminal of said source, and. lock-out contacts actuated by saidinitial movement for connecting said wire ot a busy line with the otherterminal oi said electromagnet to operate said latch when attempting toconnect with a busy line, continued movement oi? said plunger inconnecting with a non-busy line opening the connection made by saidlock-out contacts.

13in a switching mechanism of the class described, the combination of:mechanism for use at a first station for selecting and connecting withany one of a pluality of lines extending from said first station andrespectively connected with other stations, whereby operation of saidmechanism establishes communication directly between said first stationand the other selected station, electromagnetic lockout devicespermitting initial connecting movement and when actuated preventingcomplete connecting movement of said mechanism, a set of line contactsfor each of said lines, one contact of each set being a test contact,and means for establishing connection between said test contact and saiddevices by initial movement 01' said mechanism. I

14. In a switching mechanism of the class described, the combination ofmechanism for selecting andv connecting lines for conversation,electromagnetic lock-out devices permitting initial connecting movementand when actuated preventing complete connecting movement of saidmechanism, sets of line contacts, one contact of each set being. a testcontact, and means for establishing connection between said test contactand said devices by initial movement of said mechanism, continued movement of said mechanism when said devices are not operated interruptingsaid connection.

15. In a switching mechanism of the class described, the combination ofsets of contacts for lines to be connected, a plunger. switch. bladescarried by said plunger for connecting said contacts as desired, onecontact of each set being a test contact, a latch permitting initialmovement of said plunger and when actuated preventing completeconnecting movement of said plunger, an electromagnet tor actuating saidlatch, and contacts actuated by initial movement of said plunger forconnecting said test contact with said electromagnet.

16. in a switching mechanism of the class describeiil, the combinationof sets or contacts for lines to be connected, a plunger, switch bladescarried by said plunger to; connecting said contacts as desired, onecontact of each set being a test contact, a latch permitting initialmovement of said plunger and when actuated. preventing completeconnecting .movement of said plunger, an electromagnet for actuatingsaid latch, and contacts actuated by initial movement oi said plungerfor connecting said test contact with said electromagnet, continuedmovement of said plunger when said latch is not actuated interruptingsaid last named con nection.

17. In a switching mechanism of the class (lGSQ-l'lbfitl, thecombination of mechanism for selecting and connecting lines forconversation, electromagnetic lock-out devices permitting initialconnecting movement and when actuated preventing complete connectingmovement of said mechanism, sets of line contacts, one contact of eachset being a test contact, and means for establishing connection betweensaid test contact and said devices by initial movement of saidmechanism, said devices also serving to retain said mechanism in itsline connecting position.

18. In a switching mechanism of the class described, the combination ofsets of contacts for lines to be connected, a plunger, switch bladescarried by said plunger for connecting said contacts as desired, onecontact of each set being a test contact, a latch permitting initialmovement of said plunger and when actuated preventing completeconnecting movement of said plunger, an electromagnet for actuating saidlatch, and contacts actuated by initial movement of said plunger forconnecting said test con-- tact with said electromagnet, said latch alsoserving to retain said plunger in its line connecting position.

19. In a switching mechanism of the class described, the combination ofsets of contacts for lines to be connected, a plunger, switch bladescarried by said plunger for connecting said contacts as desired, onecontact of each set being a test contact, a latch permitting initialmovement of said plunger and when actuated preventing completeconnecting movement of said plunger, an electromagnet tor actuating saidlatch, and contacts actuated by initial movement of said plunger forconnecting said test contact with said electromagnet, said latch alsoserving to retain said plunger in its line connecting position, and saidelectromagnet then serving when energized to withdraw said latch andrelease said plunger.

20. in a switching merhani -m of the class described, the combination otmechanism for selecting and connecting lines for conversation,electromagnetic loch-out d vices permitting initial connecting movementand when actuated preventing complete connect-- ing movement of saidmechanism, sets of line contacts, each set consisting of but twocontacts, one contact of each set being a test contact, and means forestablishing connection between said test contact and said devices byinitial movement of said mecha nism.

21.. In a switching mechanism of the class described, the combination ofmechanism for selecting and connecting lines for conversation,electromagnetic lock-out devices permitting initial connecting movementand when actuated preventing complete connecting movement of saidmechanism, sets of line contacts, each set consisting of but twocontacts, one contact of each set being a test contact, and means "forestablishing connection between said test contact and said devices byinitial movement of said mecha nism, continued movement of saidmechanism when said devices are not operated interrupting saidconnection.

22. In a switching mechanism of the class described, the combination ofsets of con tacts for lines to be connected, each set consisting 0t buttwo contacts, a plunger, three switch blades carried by said plunger forconnecting said contacts as desired, one of said blades being a testblade and the other blades being line connecting blades, said test bladebeing in contact with one of the other blades when the plunger is in itsouter and test positions, one contact of each set being a test contact,a latch permitting initial movement or" said plunger and when actuatedpreventing complete connecting movement of said plunger, anelectromagnet ior actaating said latch, and contacts actuated by initialmovement of said plunger for connecting said test contact with saidelectromagnet.

28. In a switchin mechanism of the class described, the combination ofsets of contacts for lines to be connected, each set consisting of buttwo contacts, a plunger, switch blades carried by said plunger torconnecting said contacts as desired, one of said blades being a testblade and the other blades being line connecting blades, said test bladebeing in contact with one of the other blades when the plunger is in itsouter and test positions, one contact of each set being a test contact,a latch permitting initial movement of said plunger and when actuatedpreventing complete connecting movement of said plunger, anelectromagnet t'or actuating said latch, and contacts actuated byinitial movement of said plunger for con necting said test contact withsaid electromagnet, continued movement of said plunger when said latchis not actuated interrupting said last named connection and sep aratingsaid test blade from contact with the adjacent line connecting blade.

In witness whereof, I hereunto subscribe my name this 12th day ofOctober, A. D.

THEODORE H. N ELSQN

